Once an egg has been laid by an animal, it must undergo a period of incubation, either naturally or artificially, during which time development of the young animal takes place. Many birds for example, sit on an egg or clutch of eggs in order to regulate temperature and humidity around the egg(s), such regulation being crucial for the survival and proper development of the embryo inside each egg. Other animals utilise different sources, for example solar or geothermal energy, for this purpose. Alternatively, incubation may be carried out and/or assisted by man. Man-made incubators are well known that can hold a number of eggs and which provide artificial temperature and humidity regulation of the air around the eggs.
Many breeders and conservationists of egg-laying animals need to know whether or not the embryo is alive and developing at the proper rate inside the egg. Such knowledge is required throughout the incubation period, and is important both in natural and artificial incubation scenarios in order to maximise the chances of survival of the young. In natural incubation, for example a clutch of eggs brooded by a bird, if one or more embryos does not survive, those eggs can become infected by bacteria and endanger the remaining eggs. Furthermore, some species of parrot for example the Palm Cockatoo, Black Cockatoo and Hyacinthine Macaw, can only lay fertile eggs during a short period of time each year and even then only incubate one egg at a time. If that egg does not survive, the opportunity for successful breeding has been missed for that year. Such scenarios can have serious implications for endangered species, and for breeders and keepers of such birds who exchange them for considerable sums of money. The situation is analogous for many species of egg-laying animal.
There are two well known methods for checking the fertility and development of eggs. The first method, known as “candling”, involves placing an egg in front of an intense light source, for example tungsten halogen, so that the inside of the egg is visible to the naked eye, and looking for signs of growth e.g. vein development that is first visible after approximately four days in parrot eggs. Over the next few days it is possible to check for further growth by looking for increasing numbers and density of veins and a growing “dark spot” in the centre of the egg. However, there are three disadvantages with “candling”, the first being that a high intensity of light is required to see into the egg meaning that it is exposed to high temperature levels that can damage or kill the embryo in the egg if held over the light for too long. Secondly, the “dark spot” grows at such a rate that after approximately twelve days (in parrot eggs) it occupies so much of the volume of the egg that the veins are no longer visible and it is not possible to tell whether or not the young bird is alive. Thirdly, some eggs are not suitable for “candling” such as raptors, falcons, ducks and wild fowl, whose eggs range from dark green to dark brown in cool, and other species whose shells are so dense that the light from the lamp cannot pass through them. For such eggs it is not possible to tell whether or not they are fertile and alive in the first few days.
The second known method addresses the second and third problems mentioned above. This method involves floating the egg in still warm water and waiting for the egg to move as a result of movement of the young animal inside. There are two disadvantages associated with this method, the first being that the method is unreliable and slow since it relies on a parameter that is inherently random. Secondly, immersing the egg in water exposes it to bacteria that can pass through the shell, particularly as the egg is withdrawn from the water, when water on the surface of the egg tends to be “sucked” in through the pores of the shell severely reducing the egg's ability to self-regulate humidity. Once inside the shell the bacteria and water are in an ideal environment at 37° C. to multiply, potentially endangering the life of the young animal.
Eggs undergo differing periods of incubation. For example, chicken eggs, as used in the commercial broiler industry, have an incubation period of 21 days. After approximately 50% of the incubation period, the animal in the egg has usually grown so much that conventional candling methods will offer little assistance in determining viability.
In a commercial environment a number of methods have been proposed for determining the viability of eggs, for example white broiler chickens, viz.:
U.S. Pat. No. 3,540,824 discloses a method of candling eggs using white light. Light in the wavelength range 6.5×10−7 m to 8.5×10−7 m is transmitted along the longitudinal axis of an egg with a light source positioned on its blunt end. A photoelectric sensor is positioned on the opposite end of the egg to detect light passing out of the egg over a wavelength range 7.3×10−7 m to 7.5×10−7 m with peak sensitivity at 7.35×10−7 m. An output from the photoelectric sensor is filtered to reveal a heartbeat in the egg, if present.
There are a number problems associated with the apparatus described in U.S. Pat. No. 3,540,824 that make it unsuitable for reliable and efficient determination of the viability of eggs of at least 50% through their incubation period. Firstly, the white light source operates over a broad range of wavelengths. It will be noted that the photoelectric sensor is sensitive over a smaller range of wavelengths than are emitted into the egg by the light source, and that this smaller range borders the visible/infra-red boundary. The definition of the visible/infra-red boundary in terms of wavelength does not appear to be strictly defined in scientific dictionaries. For the purposes of the present invention it may be said to cover from more than 7.5×10−7 m (750 nm) up to 1.0×10−3 m (1 mm).
Light at visible wavelengths has a larger coefficient of absorption in tissue than light at infra-red wavelengths. The applicant has notices that the coefficient of absorption decreases as wavelength increases, such that infra-red having a wavelength in the visible/infra-red boundary will be more heavily attenuated in tissue than light with a wavelength in the middle of the infra-red part of the spectrum, for example. Accordingly, in order to obtain a signal with a detectable heart rate over the comparatively narrow range of wavelengths that the photoelectric sensor is sensitive, the light source must be relatively intense (one half or higher candle power is suggested in U.S. Pat. No. 3,540,824). As mentioned above, emitting intense visible light at the egg has an undesirable heating effect that can endanger the egg.
Secondly, as the embryo grows in the egg, more and more of the light from the light source will be absorbed for a given light intensity. The applicant has discovered that this problem is particularly acute in eggs of more than approximately 50% through their incubation period, for example 10 or 11 days in chicken eggs. Hence in the apparatus of U.S. Pat. No. 3,540,824, where both the light source and sensor lie on the longitudinal axis of the egg, a point will be reached where the sensor receives no useful signal. This problem is even more acute in chicken eggs of 16 to 18 days into incubation, just when viability needs to be determined for vaccination or gender sorting purposes for example. One way to deal with this might be to simply increase the intensity of the white light. However, this is highly undesirable for the reasons given above.
Thirdly, U.S. Pat. No. 3,540,824 mentions that movement of the chick affects the IR radiation received by the photoelectric sensor. It is stated that this does not affect operation of the apparatus in detecting a heartbeat. However, the applicant has found that this does not appear to be the case i.e. when the chick moves the applicant has found that it is not possible to detect the heart rate. Whilst is acknowledged by the applicant that the heartbeat will almost certainly be superimposed on the variation due to movement, the variation in the light intensity due to movement is so big that detection of heartbeat is very difficult while the chick moves.
JP-A-9 127 096 discloses an apparatus for determining the viability of a young egg, less than 10 days into its incubation period. Such eggs are much more transparent to light. The document does not say what type of light should be used, but it is clear that the light passes all the way into the egg, is scattered inside and is detected upon leaving the egg. Such methodology will not work reliably on eggs more than approximately 50% through their incubation period.
SU-A-1 597 173 discloses an apparatus for determining the viability of a young egg, less than 10 days into its incubation period. The document suggests that infra-red light be emitted through the pointed end of the egg, to be scattered inside the egg, and received back at the pointed end of the egg. Such methodology will not work reliably on eggs more than approximately 50% through their incubation period.
As acknowledged in U.S. Pat. No. 4,955,728 and U.S. Pat. No. 6,234,320 it is known to treat poultry embryos in ovo with, medication, nutrients and hormones, for example. This has the advantage that the appropriate treatment, for example vaccination, can be automated rather than given to the chick by hand shortly after hatch, thereby reducing costs. These methods are employed in the commercial poultry industry to decrease post-hatch mortality rates or increase growth rates of the hatched bird, for example. Typically, poultry eggs are injected on day 18 of their 21 day incubation period. Eggs are held in trays on racks in carts for incubation in relatively large incubators. At a selected time, typically on the 16th, 17th or 18th day of the incubation period, a cart of eggs is removed from the incubator for separating out non-viable eggs i.e. those that are dead or were not fertilised, from viable eggs. Those eggs that are determined to be viable are then sorted by gender or inoculated for example.
It is important to determine whether an embryo is alive or not in the egg before the relevant treatment is given. This is for a number or reasons including the financial cost of treating dead eggs and the fact that many dead eggs become infected with bacteria. If an injection system penetrates such a dead egg there is a high risk that the system will contaminate live eggs subsequently with this bacteria.
It is also desirable to sort birds by gender, particularly poultry, as described in WO-A-98/14781 for example. It is even more advantageous if this can be done before the bird hatches, i.e. in ovo, as considerable time and resources can be saved.
In performing vaccination and gender sorting as described above it is important that the available resources are used on viable eggs i.e. those that are alive. In many instances, an egg may not have been fertilised or may have died during incubation. It is important that these viable eggs are removed from the batch so that incubation, vaccination and gender sorting resources are not wasted on them. It is possible to remove the non-viable eggs. However, these have a tendency to “pop” when handled if they contain methane. The methane is generated by bacteria that infect the egg, putting the egg under gas pressure and making it especially fragile. If an egg bursts it may contaminate viable eggs, and so it is preferable to remove the viable eggs from the batch.
Heretofore, it has been difficult to reliably and quickly sort eggs that are alive from those that are dead, particularly in the commercial poultry farming industry.
Thus, it is apparent that there is a need for an apparatus and method of testing the viability of eggs from at least approximately 50% through their incubation period up to hatch that is more reliable, that minimises the risks to which prior methods have exposed eggs, and that does not require eggs to be positioned in a particular position during incubation and/or testing. Furthermore, there is a need for such an apparatus and method in which it is possible to distinguish between light intensity variation due to action of a heart and light intensity variation due to movement of the animal. There is also a particular need for a method and an apparatus that can determine the viability of a poultry egg when the egg is approximately 16 to 18 days into its incubation period of 21 days, prior to vaccination or gender sorting for example. There is yet a further need for a method and apparatus that provide an increased level of confidence in the result of a viability test on an egg or eggs.